New Trends in Beverage Packaging Systems: A Review

New trends in beverage packaging are focusing on the structure modification of packaging materials and the development of new active and/or intelligent systems, which can interact with the product or its environment, improving the conservation of beverages, such as wine, juice or beer, customer acceptability, and food security. In this paper, the main nutritional and organoleptic degradation processes of beverages, such as oxidative degradation or changes in the aromatic profiles, which influence their color and volatile composition are summarized. Finally, the description of the current situation of beverage packaging materials and new possible, emerging strategies to overcome some of the pending issues are discussed

New complexes of chromium(III) containing organic π-radical ligands: An experimental and density functional theory study

The electronic structures of a series of chromium complexes 1–7 have been experimentally investigated using a combination of X-ray crystallography, magneto- and electrochemistry, and Cr K-edge X-ray absorption and UV–vis spectroscopies. Reaction of the dimer [CrII2(μ-CH3CO2)4]0 with 2,2′-bipyridine (bpy0) produced the complex [CrIII(bpy0)(bpy•)(CH3CO2)2]0 (S = 1) (1), but in the presence of isopropylamine (iPrNH2) [CrIII(bpy•)(iPrNH2)2(CH3CO2)2]0 (S = 1) (2) was obtained. Both 1 and 2 contain a CrIII ion and a single (bpy•)1– ligand, so are not low-spin CrII species. One-electron oxidation of 1 and 2 yielded [CrIII(bpy0)2(CH3CO2)2]PF6 (S = 3/2) (3) in both cases. In addition, the new neutral species [CrIII(DAD•)3]0 (S = 0) (4) and [CrIII(CF3AP•)3]0 (S = 0) (5) have been synthesized. Both complexes contain three π-radical anion ligands, which derive from one electron reduction of 1,4-bis(cyclohexyl)-1,4-diaza-1,3-butadiene and one electron oxidation of 2-(2-trifluoromethyl)-anilino-4,6-di-tert-butylphenolate, respectively. Intramolecular antiferromagnetic coupling to d3 CrIII gives the observed singlet ground states. Reaction of [CrII(CH3CN)6](PF6)2 with 2,6-bis[1-(4-methoxyphenylimino)ethyl]pyridine (PDI0) under anaerobic conditions affords dark brown microcrystals of [CrIII(PDI0)(PDI•)](PF6)2 (S = 1) (6). This complex is shown to be a member of the electron transfer series [CrIII(PDI)2]3+/2+/1+/0, in which all one-electron transfer processes are ligand-based. By X-ray crystallography, it was shown that 6 possesses a localized electronic structure, such that one ligand is neutral (PDI0) and the other is a π-radical monoanion (PDI•)1–. Again, it should be highlighted that 6 is not a CrII species. Lastly, the structure of [CrIII(Mebpy•)3]0 (S = 0) (7, Mebpy = 4,4′-dimethyl-2,2′-bipyridine) has been established by high resolution X-ray crystallography and clearly shows that three (Mebpy•)1– radical anions are present. To further validate our electronic structure assignments, complexes 1–6 were investigated computationally using density functional theory (DFT) and found in all cases to contain a CrIII ion. This oxidation state assignment was experimentally confirmed for complexes 2, 4, 5, and 6 by Cr K-edge X-ray absorption spectroscopy

Intramolecular Redox-Active Ligand-to-Substrate Single-Electron Transfer: Radical Reactivity with a Palladium(II) Complex

Coordination of the redox-active tridentate NNO ligand L-H2 to Pd-II yields the paramagnetic iminobenzosemiquinonato complex 3. Single-electron reduction of 3 yields diamagnetic amidophenolato complex 4, capable of activating aliphatic azide 5. Experimental and computational studies suggest a redox-noninnocent pathway wherein the redox-active ligand facilitates intramolecular ligand-to-substrate single-electron transfer to generate an open-shell singlet "nitrene-substrate radical, ligand radical", enabling subsequent radical-type C-H amination reactivity with Pd-II